Scraper structure for liquid treatment tanks



v Spt. 9, 1941. E, A, 'KAMP 2,427,092

SCRAPER STRUCTURE FOR LIQUID TREATMENT TANKS Filed Aqg. 26, 1944 s sheets-shes: 1

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Patented Sept. 9, 1947 UNITED STATES PATENT OFFICE semen snows FOB mourn Ewald A. Kamp, Chicago, Ill., acllg'nor to Graver Tank & Mfg. 00., Inc, a corporation of Dela- This invention relates to liquid treatment and particularly to sludge removal devices for clariflcation tanks of large area and capacity. It is an improvement overthe invention of A. C. Durdin III, covered by the copending application, Serial No. 507,631, filed October 25, 1943.

It is an object of this invention to provide such devices which are relatively inexpensive while being eflicient, adaptable to tanks of different types and sizes, and free from features interfering with other structures in such tanks. The and other objects will be more clearly understood upon consideration of the detailed description which follows, in connection with the drawing, wherein: g

Fig. 1 is a central sectional elevation of an embodiment hereof;

Fig. 2 is a plan view of the apparatus shown in Fig. 1. v

Fig. 3 is a sectional detail taken along lines 3-! in Figs. 1 and 4.

Fig. 4 is a further section taken along lines 4-4 in Fig. 3.

I The'drawing shows a circular clarification tank It having a cylindrical side wall ll, substantially flat, circular bottom It, and open top. Raw liquid enters through the pipe i3, and treated liquid is withdrawn over weirs l4 installed adjacent to the top of the tank, but slightly below said top, in a horizontal plane.

Since the invention .relates to a tank of large area, wherein diiliculties are encountered if an attempt is made to withdraw clarified liquid over a single, annular weir, a plurality of such weirs I! are shown, concentrically with one another and with the tank. It will be understood that these weirs may have either straight top edges or spaced V-notches, or other similar expedients. The important thing is that the several'weirs are so arranged with respect to the. clarification zone It within the tank It that excessive flow velocities are avoided throughout this zone. For this purpose, I preferably install the several weirs so that each of them has, next adjoining to it, a partial, annular, concentric tank area II, II, I 8, constituting a substantial portion of the totalarea of the clarification zone II; the sum of these partial areas being equal to the total area. when referring to a substantial portion, I mean, in general, an approximately proportional portion; for instance. with three welrs H as shown, each area l8, l1. and It would. cover approximately onethird of the total area of the clarification zone II. This arrangement, however, is subject to modification, inasmuch as the weirs have different lengths, being concentric circles around the common center. Also, for best results, it is necessar to consider distance of horizontal travel of 5 Claims. (01. 210-55 the outgoing liquid towards the weirs,, as well as the area available for the flow rising to the several weirs. For-[such reasons, it is frequently desirable to have the innermost weir M installed a 'more closely adjacent the center of the tank than would be required for a strictly uniform area associated with each weir. Furthermore, any V-notches distributed along the several weirs are preferably more closely spaced in the inner weirs than in the outer ones, to insure substantially uniform withdrawal of liquid.

This arrangement of concentric weirs has substantial advantages. particularly in a tank having an open top exposed to the influence of wind;

and the clarifying capacity of a tank is greatly increased thereby. However, various difiiculties heretofore prevented the use of such concentric weirs. Theseveral weirs, of course, areassociated with annularlaunders It; a plurality of go concentric launders being shownin the present embodiment. While the outermost launder l 9 and weir .Il may be supported from the tank wall Ii, in manner to be described hereinafter, it is a further question how the interior launder or launders, with their weirs, should be supported.

In this connection, it must be kept in mind that i a tank of this type requires sludge scrapers 20, which are most desirably pivoted above the liquid level, in the center of the tank, and driven in a go slow motion which should be as uniform and quiet as possible, to avoid disturbance of the process of clarification. The most desirable type, in this respect, involves a motorized traction wheel installed adjacent the periphery of the tank, and

as various structural members, whereby the scrapers and traction wheel are associated with one another and with the tank.

The .present embodiment comprises a large cylindrical baille wall or partition 2! positioned above a peripheral part of the bottom l2, that is installed relatively adjacent to the outer wall i I. This wall extends from the top of the tank downwards to a level spaced above the bottom II, for purposes to be described hereinafter; the clarification zone ll beingarranged inside of this baiile, and a channel or coagulation zone 22 being arranged outside of the same. This annular baiile wall II is supported by horizontal tension members 28 adjacent the top 01' the tank, and inclined to compression members 24 extending inwardly from the'oorners II between the outer wall Ii and the bottom It, which corners may be filled in with a corner fill 2| of concrete. The sludge scrapers 20 operate over the whole of' the bottom i2, except for limited area covered by such comer fill.

The outermost eilluent launder It is supported on the inside of the annular bailie II and has a single weir ll, on the inside thereof. In addition,

. 3 I provide an inner launder I9 spaced from the ballle wall 2| and having a weir I4 on the outside and one on the-inside thereof. This inner launder is supportedflfrom the annular partition 2| by means of structural trusses or support means 21 inwardly extending from the baille wall or partition 2 I, above the bottom I2.

The scrapers 28 arev carried by truss elements 28 and 29, extending outward and inward, respectively, from the bottom of astructural member 39 and forming, together, .a single; radial scraper assembly, arm, or truss for tank I3; the outer part 28 of this assembly extending below the launder support structure and inner launder 21, I9. The member "extends upwardly from the point of juncture of these scraper truss elements to ya part of thetanksurrounded by and adjacentto the inner launder I 9 1ab ovethe weirs I4. There it is secured {to .further truss 3| which extends substantial y horizontally above said weirs, from the center togthe periphery of the tank Ill. The members 28, 29, 33, and 3| form a substantially rigid scraper assembly, which in principle has the shape of a large, extended,

, Roman letter I, with long cross-strokes or serifs. This scraper assembly is supported by the upper"serifs, that is,-by the upper truss 3|, by means including rollers 32 secured to this upper truss and running on annular tracks 33 installed in conventional manner,

While the scraper assembly is substantially rigid in itself, it may comprise pivot members and adjustments as illustrated at 34 and 35 respectively, for proper adjustment. The scraper assembly is centered and held radially with respect to the tank by means of a pivot 38 at the inner end of the upper truss 3I. It is driven by a motorized traction wheel 31 installed remotely from the tank center and relatively adjacent the outer wall I I, which traction wheel in the present embodiment contacts the inside of the outer launder I9, below the water level determined by the weirs It.

Instead of being fastened to a central pivot 35, the scraper assembly can be held in radialposition by means of flanges 38 on the rollers 32, engaging flanges 39 on the tracks 33, as shown in Figures 3 and 4, or in other, well-known ways.

Three sets of rollers 32 are shown, operating over three tracks 33, with a pair of rollers 32 on each track. .One" track and set of rollers is located adjacent toand directly supported by the outer tank wall II. One is located adjacent to and directly supported by structural means in the central part of the tank. The third is located between these two, adjacent the innermost launder I9, and supported by that launder. If the weight ofthe structural parts 28, 28, 29 and 30 is insignificant, as compared with that of the upper truss 3|,the intermediate rollers 32 can be omitted, on the other hand if the weight of the up- 3| is relatively insignificant, as com- ,with that of the parts 23, 28, 29 and 38, utermost rollers 32 can be omitted.

M ferably, however, all three sets of rollers are used, as, shown. In this event, most of the weight ot'tlie, scraper assembly is carried by the intermediate and innermost rollers, and the outermost rollers, carry only about one-half of the weight of the outer part 3l-B of the upper truss 3 I. This part '3 I'B, and the inner part 3 I-A of the upper, truss 3|, is mainly, if not exclusively, relied upon to provide rigidity in a horizontal plane, whereby the peripheral drive, wheel 3'! can drive the scraper assembly against the load due to the re of said assembly. This tilting component can be restrained .in various manners, one of which is shown inFigs. gg and 4. A roller 40 engages the intermediate tr'ack'33 from below, and is secured to the truss 3i so that it may serve as an antitilt toilet, in manner well understood in the art. The drag on the vertical structural member 30. induced by the sludge load on the scrapers 20, tends to induce a tilting of the structural member but the member 3Il is restrained by this antitilt roller, so'that'the intermediate support rollers 32 stay safelyon their track 33, and the top truss 3| can not be twisted. Similar anti-tilt rollers could be installed adjacent the aforementioned end rollers 32, but in that event, the truss 3I would have to be made stronger and heavier.

The raw water inlet I3 discharges into the tank I0 adjacent the center thereof, and the liquid enters a centralfmlxing chamber 4|, which is separated'fromlthe clarification zone I5 by means of a cylindrical partition '42 extending from the bottom to the top of the tank and forming a central, hollow pier in the tank. In this mixin chamber, the incoming liquid is mixed with chemicals received through the feed pipe 43, the materials being mixed by a rotary propeller 44, which is actuated by a drive mechanism generally indicated at 45, through a shaft 46. The mixed materials are received, at the bottom of the mixing chamber, in a series of radial transfer pipes 41, extending below the bottom I2 of the tank, and merging into vertical pipes 48, adjacent the tank periphery, which vertical pipes discharge into an upper part of the coagulation chamber 22.

In the present embodiment, the central partition 42 has openings 49 in the upper part thereof, and is surrounded by a cylindrical partition 58 extending from the top to above the bottom of the tank, sothat upon rotation of the propeller 44, there is established and maintained a fluid circulation or recirculation downwardly through the mixing chamber M, then through the ducts 41 and 48, coagulation chamber 22, lower part of the clarification chamber I5, and drum 5!] back into the mixing chamber H. The advantage of this recirculation is that substantially perfect distribution of the liquid and suspension of some of the sludge, in the clarification zone I5, can be maintained at all times, irrespective of variations in the rate of liquid input through the pipe I3; aside from the fact that the results may be improved in well-known manner by starting and completing the chemical treatment in the presence of sludge previously formed in liquid of the same kind. It will be understood that the concentric launders as described are particularly useful in connection with this method of distributing the liquid and suspending the sludge in the clarification zone.

While large amounts of sludge may be suspended and recirculated in this manner, all of the sludge ultimately settles. on the bottom I2, and is collected by the scrapers 28, in a conventional sludge sump 5|, which is preferably formed ina relatively central part of the bottom I 2, and

drained by a pipe 52 in well-known manner.

The central partition 42, among other things,

serves as a structural support for the track II; pivot a and agitator drive 45.

In some instances there is a tendency for scum and other floating matters to accumulate on topof the co ulation channel 22. Such matters: can be removed by a scum blade 53, cooperating; with other known devices (not shown), in manner well:

understood in the art.

The drive wheel I1 is suitably motorized and supported, in manner known from other com structions, and rotates to drive the whole scraper assembly around the center of the tank. By means of the I-shaped construction of the scraper assembly, interference between the structural members 21 and 30 is avoided, while desirable types of eifluent weirs and scraper drives are used. If the vertical member 30 were located adjacent the center or periphery of the tank, additional weight would be required for the truss that would take the place of the scraper arms 28 and 29, since this-truss would cantilever from the vertical member over the entire length of a radius of the tank, unless objectionable, submerged rollers were used. Furthermore, a centrally located, vertical member would be conducive to an objectionable "whipping" tendency of the scraper assembly. A peripherally located, vertical member would make it impossible to use the necessary inner weirs and overflow launder, unless these were supported and connected through a central structure, which is complicated and undesirable.

It will be observed that in the present construction, a single scraper arm or assembly is radial- 1y installed in the tank, to rotate over the bottom of the tank. Previously, it was usual to provide at least two radial scraper arms and sometimes four or more, for the purpose of balancing such arms around a central pivot in the tank. No such balancing is required in accordance herewith,inasmuch as the I-shaped scraper assembly'is safe- 1y supported by the expedients shown and described. Considerable material can be saved in this manner. Furthermore, it is possible to standardize, inasmuch as practically all tanks in accordance herewith may be equipped with the same type of motorized drive wheel 31, support rollers 32, and anti-tilt rollers 40. Finally, a

I cipitatedi sludge into said sump; structural means extendingupwardsi'romsaidtrussto apart of the tank surrounded by and, located above said launder, and further extending, above said launder and support means, towards said peripheral wall; structural means and truss. being rotatstructural means extends from said part of the tural means and truss tank surrounded b and located above said launder, to said pier as well as towards said baiiie wall, and is rotatably supported by the top of said pier; and wherein said sludge scraper truss extends inwardly away from said structural means, as well as below said support means; so that said struc- I forms a substantially I- shaped assembly.

3. A tank according to claim 1 wherein said means to rotate said structural means and truss single radial scraper has operating advantages over a plurality thereof, particularly in a tank providing circulating flows over the bottom, inasmuch as every scraper assembly unavoidably defleets and disturbs the liquid flow overthe bot-- tom, and such disturbance is minimized by a minimum number of scraper trusses.

It will be obvious to persons skilled in this art, upon consideration hereof, that various modifications can be applied.

I claim:

1. A tank for liquid treatment by the precipitation of sludge, comprising a flat, circular bottom; a sludge sump in said bottom; a peripheral wall; an annular baiile wall positioned above a peripheral part or said bottom within said peripheral wall to form an outer channel and an inner zone,

the bottom oi said channel communicating with Y the bottom of said zone; at least, one annular launder horizontally positioned in and concentric with an upper part of said tank and inwardly spaced from said baiile wall to provide overflow means for treated liquid; a plurality of support means inwardly extending from said baiile wall, above said bottom. to support saidv launder; a sludge scraper truss radially extending adjacent said bottom and below said support means;-

sludge scraper means on said truss to scrape pre- 'is installed on the portion of said structural means extending above said launder and support means.

4. A tank for liquid treatment by the precipitation oi sludge, comprising a flat, circular bottom:

a sludge sump in said bottom; an upright, annular wall positioned above a peripheral part of said bottom: annular track means adjacent the top of said wall; a plurality. of annular launders horizontallypositioned in and concentric with an upper part of said tank, at least one such launder being inwardly spaced from said wall, to provide overflow means for treated liquid; a plurality of support means inwardly extending from said wall, above said bottom, to support said spaced launder; a sludge scraper truss radially extending adjacent said bottom and below said support means; sludge scraper means on said truss to scrape precipitated sludge into said sump; structural means extending upwards from said truss to a part of the tank surrounded by and located above said spaced launder, and further extending,

above said launders and support means, towards said wall and track means; said structural means and truss being rotatable in a path around the center of the tank; means installed on said structural means and engaging said track means to rotate said structural means and truss over said path; and liquid inlet means in a central part of the tank.

5. A tank according to claim 4, comprising additional track means on said launder, and roller means supported by said additional track means and cooperatingto support said structural means and truss.

EWALD A. KAMP.

REFERENCES CITED The following references are of record in the file of this patent:

v imrrnn s'rs'rus ram-rs Number Bousman Dec. 31, 1929 

